I'm shocked only one person has said it! Ai Yori Aoshi takes the cake next to Clannad. Ai Yori Aoshi manged to give the viewer a sense of romance most animes established by kissing & groping. Ai Yoshi Aoshi & Clannad are similar in a sense where the tone & romance isn't set by kissing or sexual situations.

Other than that, Ano Natsu de Matteru & Eureka 7 take some of the cake as well.

The last 40% chunk of this cake goes to my 3rd favorite anime, EVER: Blast of Tempest.

The anime is legit sound in almost every aspect. It tests the viewers psychological standpoint & has beautiful character development as well as environment development. While most animes take place in a high school, this one takes you to some crazy & odd looking places that fit perfectly with the storyline. The storyline & plot itself are based off the Shakesperian play which is adapted perfectly in the anime. I recommend it to all. Every loose end was tied up by the end as well, which is hard to get from a LOT of romance animes.

5 Centimeters per second
Voices of a distant star
Chobits
Toradora!
Clannad(Both seasons)
Hotarubi no Mori e
Welcome to the NHK(More the Manga than the Anime, its a really messed up relationship though.)

I liked Kare Kano (His and Her Circumstances). I enjoyed the fact that it didn't take an entire season to have the main characters get together. I liked that they showed how their relationship grew and matured as the series went on. To avoid getting stale, the show also developed other characters and saw them starting their own relationships. While I can't say I dislike a particular show, I do feel a little cheated when they take the entire season to get them together and then it's over. I like to see the relationship become more.

Toradora was good as well, but I didn't like that we don't get to see much beyond them getting together. I know people may read this and say "well, go read the mango for more." Yeah, I know there is more in the manga just as there was with Kare Kano, but it peeves me a little when you develop an anime and only produce a single season when it only tells a small piece of the story. Kare Kano was 26 episodes if I remember correctly (I may be wrong) and it bugged the hell out of me that there was no real ending and doubt we will ever see a season two.

Nana was another great anime that didn't get a proper ending, although it's understandable since Ai Yazawa got sick.